Which is more efficacious: +3 or +2 with a boost?

[Spatzimaus]

I have thought about one other reason why flaming weapons might be good - take a look at the rules for swarms. A good many are immune to weapon damage, although elemental damage on a weapon applies normally.

Ooh, hadn't thought about them. Although, from the way the rules look I'd still just let the wizard blast the swarm with a Fireball instead of trying to 1d6-it to death. But yes, that's an advantage of the elemental ones.

Another advantage is that you can set stuff on fire with a Flaming weapon. Stick some marshmallows and hot dogs on the end of the sword, say the command word, and you've got yourself the makings of a nice camping dinner. Can't do that with an Enhancement bonus.
Each of the others has a similar effect. Use a Frost weapon to keep your beer cold (your "sheath" could just be a large flask... dang, now I want a Dagger of Frost for my character). If you don't like beer, you can still make popsicles this way. Stick your frost weapon in the refrigerator to keep it cold. There's also the Spiked Gauntlets of Frost. Activate them and whatever beer you're holding gets nicely chilled, with the cup insulating it from freezing.
For Shock weapons? Get a Shuriken of Shock, and palm it. Shake hands with someone. Instant joy buzzer! Hey, it explicitly says YOU don't take damage from it, after all. Of course, if the other person is a 1HD Commoner they'll probably die from it, but humor is never safe. For the more serious people, I have to wonder: how many Shock weapons going at once does it take to provide enough power for an Industrial Revolution?

 

[Voadam]

So I have a 12th level ranger focued on archery. Should I get a +3 bow or a +2 bow with (insert your effect here)? Which one and why?

I'd go with wierd abilities over straight plusses because they make things more interesting than a straight buff.

If you choose an energy effect sometimes it will let you do things where your normal magical arrow wouldn't, sometimes it will hit a monster vulnerability, and sometimes it will be nullified by resistance or immunity.

But that variety makes for more interesting situations where you can shine more or face tougher adversity keeping challenges dynamic.

 

[SpikeyFreak]

If you have excel you can check the actual numbers with the excel sheel linked in my sig.

--Busy Spikey

 

[two]

Limiting Cases

It might help, or not, to think about the extremes...

If you have a +2 weapon that does a point of weapon damage per hit wielded by a str. 10 human, then you want to get a 1d6 energy enchantment for sure. You don't care about hitting (you only do 3 damage per whack), what you care about is when you DO hit you do 3+3.5 damage, which is worth more than 2 normal hits. So get rid of the +1 to hit/+1 damage and go for elemental boni.

However.

If you have a huge honkin' +2 weapon doing 3d8 damage, with a strength of 30, each whack is 3d8+17, averages about 30 per hit. You could care less about a measly 3.5 additional elemental damage;what you really want to do it hit more often (because it does sooooo much damage). Go with the increased enchantment level (+3/+3).

Does that help is this ranger archer situation? Probably not.

 

[Hypersmurf]

And Artoomis: as I mentioned above, that "must have a higher Enhancement bonus to Sunder" rule isn't in 3.5E. At least, I can't find it in the SRD.

It's there - it's just in a different place.

"Hardness and Hit Points: An attacker cannot damage a magic weapon that has an enhancement bonus unless his own weapon has at least as high an enhancement bonus as the weapon or shield struck. Each +1 of enhancement bonus also adds 1 to the weapon’s or shield’s hardness and hit points."

You'll find it in "Magic Items II - Weapons and Armor", under Magic Weapons.

-Hyp.